Mining Lignite Coal for our Energy Future

Dragline rolls to new location in first act of BNI's big move

A Page 736 dragline, weighing about 2 million pounds, was lifted onto a special wheeled vehicle and moved to a new location at the mine site near Center, N.D., late Friday.

But last week’s move—as big as it is—is only the warmup for this week’s event. That’s when Liberty—BNI’s 9-million-pound dragline—will be on wheels. It will be the first time a dragline the size of Liberty is moved by a wheeled vehicle in North Dakota.

“The whole relocation process went very smooth,” said Wade Boeshans, general manager of BNI. “Our team did an exceptional job planning and communicating throughout the process. The contractor, Mammoet, was very well organized and demonstrated exceptional knowledge and expertise. I am very pleased with our team’s willingness to think creatively and take a risk. They navigated it all masterfully.

Both draglines are being moved as the lignite mine expands. Last year, the number of acres under permit at the Center Mine doubled to about 18,000 acres, and the draglines are being moved to Area C, about four miles south of the Milton R. Young Generating Station. The draglines remove the top layers of earth to expose the coal seams. They don’t actually dig the coal, but they make it possible for BNI to extract and deliver about 90,000 tons of coal a week. Nearly all the lignite coal mined by BNI is consumed at the Young station.

Mammoet, a Dutch company known as a world leader in engineered heaving lifting and transport, was hired to haul the two draglines on specially configured “self-propelled modular transporters.” These transporters have hydraulically-driven wheels pinned together lengthwise in “trains,” each powered by a 600-horsepower engine. Moving Liberty, a Bucyrus 8200 dragline, will require seven trains of transports 65 feet wide, with 197 axles and 877 pneumatic tires. The Page dragline requires 36 axles and 177 tires.

First, a series of 500-ton climbing jacks are placed around the dragline so the giant shovel can be lifted six to eight inches to make room to place the modular transporters underneath.

Liberty and the Page dragline are each equipped with a “walking” apparatus that can propel them by way of gears and camshafts connected to two huge mechanical “shoes.” After much analysis, BNI officials determined it would be more efficient, safe and cost-effective to transport the draglines rather than “walk” them as is traditionally done.

For one thing, using the modular transporters to move an enormous dragline is much faster than walking it—about one mile per hour compared to about seven feet a minute. Walking the draglines would be hard on the equipment and require more road construction and environmental expenditure. For most of the journey, the transporters will be able to roll down a BNI haul road.

During their eight-mile journey, the draglines must get past four high voltage power lines, including the DC Line that moves electricity from the Bison Wind Energy Center to a substation near Duluth. The power lines will be lowered before the draglines reach them and raised again afterward. A bridge and county road will be bypassed, and BNI built a special haul road to negotiate Hagel Creek.

Mammoet gained fame as a mover of heavy equipment in October 2000, when it was awarded a contract to salvage the Russian submarine Kursk, which exploded and sank in the Barents Sea. The company managed to lift the sub off the sea floor and bring it to the surface. Unexploded torpedoes, cruise missiles and two nuclear reactors were on board the vessel.